What Types of Lighting are used to Internally Illuminate Signs?

The three primary types have been fluorescent, neon and LEDs for at least two decades, but the ratio of each has drastically changed. An industry trade journal, Signs of the Times, has traditionally tracked these changes through industry surveys. Its most recent such survey was published in its March 2015 edition. It notes that (Table 4), in 2014, sign companies reported that LEDs illuminated nearly 60% of all electric signs. In contrast, that figure was 14.7% in 2006. Over that same time period, the percentages for fluorescent and neon dropped from 44.5% to 25.6% and from 34.1% to 12.3%, respectively. The full report can be read in that magazine's online, digital edition at the following link.  http://www.nxtbook.com/nxtbooks/STMG/sott_201503/index.php#/76.